Muffler and silencer



'Mah 30; 1954 A. KIMBAL MUFFLER AND SILENCER Filed Aug. 25, 1952 FIG. 2

IN VEN TOR.

Patented Mar. 30, 1954 UNITED STATES PATENT O F FIC E MUFFLER AND SILENCER Alfred Kimbal, San Francisco, Calif.

Application August 23, 1952, Serial No. 305,932

1 claim. 1

My invention relates to improvements in muiiiers and silencers in which a gas carrying sound waves flows through a number of chambers, diffusers, and ducts of original design and arrangement, providing a very large cross-sectional area with a corresponding slowing of the velocity of the flow; and the objects of my improvement are first, to diminish the intensity of these sound waves-mainly by their neutralization but also by dissipation'and/or absorption; second, to lower the pressure peaks of the gas if the ow is intermittent, and thus make the flow more nearly continuous; third, to avoid building up back pressure on the gas.

I attain these objects by the device illustrated in the accompanying drawing, in which- Figure 1 is an end View of the entire device; Fig. 2, a side elevation and section'on line 2 2. Fig. l; Fig. 3, a front elevation and section on line 3-3, Fig. 1; and Fig. 4, a section on line i-IL Fig. 3.

Similar numerals refer to similar parts throughout the several views.

A cylindrical housing I has its ends covered by circular end plates 2 and 3. An inlet pipe 4 is'attached to and passes through the center of plate 2, and an outlet pipe 5 is similarly attached to plate-3.

Expansion chamber 6 is shaped like the frustum of an oblique cone. Its larger base is attached to end plate 2 and just includes the inlet pipe 4 opening. Its smaller base is attached to end plate 3 and just excludes the outlet pipe 5 opening. It is perforated all around and from end to end to distribute uniformly over its entire area and with minimum back pressure the gases vpassing through it into four receiving chambers adjacent to it. In chamber 6, the gases expand andsound waves are repeatedly reflected from the end walls and from between the perforatons on the inside surface of the conical frustum.- Under these conditions, sound waves are partially neutralized.

The gases emitted from chamber 6 are uniformly distributed to the four surrounding receiving chambers. There are two symmetrical pairs from the walls of which'the sound waves are repeatedly reflected. Each of one pair of receiving chambers is bounded by one-quarterofthe inside wall of housing I, one-quarter of the outside wall of expansion chamber 6, end plates 2 and 3, and one leg of bracing plate 1 or 8. Each of the other pair of receiving chambers is bounded by one-quarter of the outside wall of expansion chamber 6, both legs (which are perpendicular to each other) of angular bracing plates 'I or 8, and part of the exterior wallv of accumulator chamber I0. This arrangement retards the sound Waves carried by half of the gas in the first pair of receiving chambers in relation to the sound waves carriedby the other half of the gas enteringfvthe second pair of receiving chambers directlyfrom expansion-chamber Grand therefore causes maximal sound wave interference in the second pair of similar chambers where both halves of the gas are reunited.

Angular brace plates l and 8 are attached to parts 2, 3, E, and i9. Brace plates 'I and 8 have theirV entire surfaces perforated to distribute gases passing through them uniformly over their entire area and with minimum back pressure on these gases.

After passing through the second leg of brace plates 'I or 3, the gases pass into two additional symmetrical chambers bounded by one leg oi parts I or 8, portions of the exterior wall of accumulator chamber I0, portions of the interior wall of housing I, and end plates 2 and 3. Each of these similar chambers is converged by the wall of housing I approaching the wall of accumulator chamber I, terminating in an elongated rectangular slot divided by three of the supports of the sixty degree V-shaped perforated diffuser plate 9 into four equal rectangular apertures along each side. The cross sectional area of this passage at its most constricted section on each side should preferably be no greater than the cross sectional area of the inlet pipe 4. The reflection of the sound waves from the walls of this converging structure causes maximum wave neutralization with minimum back pressure on the carrying gases. The head-on collision of the gases when they enter the next chamber also causes maximal wave neutralization.

The gases from both sides now unite in a chamber bounded by diiuser plate 9, housing I, and end plates 2 and 3. Part 9 is attached to parts I0, 2, and 3. Part 9 is perforated to distribute the gases passing through it uniformly over its entire area and with minimum back pressure on these gases. The sound waves reflected from the sixty degree convergent walls of part 9 suffer maximum wave neutralization with minimum' back pressure on the carrying gases.

The gases entering accumulator chamber I 0 from perforated diffuser plate 3, flow into a cir` cular section from both sides of diffuser plate 3 and thus are brought into headon collision in chamber Iii, causing maximum sound wave neutralization. Chamber It is the frustum of an obliquecone and has a smooth unbroken surface,l except for the sixty degree slot from one base to the other in which diffuser plate $3 is attached. Accumulator chamber It is also attached to parts 2, 3, 6, i, and 8. The larger base of chamber Iii is attached to plate 3 and just in' I' motion ofithegases. in chamber Il .is perpen` dicular to the axis of the outlet pipe 5, only the pressure of the gases is forcing them out; that is, any inertia the particles f gas had due to their velocity has a direction that makes it ineective to hasten the escape of the gas through the outlet pipe 5. Accumulator chamber I0 thus functions as an accumulator of the gases before passing through outlet pipe 5, making the flow of the gases leaving it more nearly continuous. For these reasons, that is, the contraction of the gases and their more continuous iiow, the outlet pipe might have a smaller cross-sectional area than the inlet pipe 4. Y

At each end of the cylindrical housing l, a small hole is provided to permit drainage of any liquid that might collect therein. For this to function when the `axis of the cylindrical housing I is horizontal, these holes would have to be at the bottom.

In using this device as a gun silencer, clearance tubes must be provided through the walls oi parts 6 and lli for the bullet, and from plate 2 through the entire device and plate 3 for sightlng.

The accumulator chamber I0, as described and illustrated, might contain within it a similar smaller accumulator chamber with its slot placed remote from the slotted side of the outer accumulator chamber. Then the inner wall of the outer accumulator chamber and the outer wall of the inner accumulator chamber would, with the circular end plates, form two similar convergent Lducts of elongated rectangular section, to convey the gas to the slot of the inner smaller accumulator chamber from both sides. Any desired number of similar accumulator chambers can be similarly placed within an outer accumulator chamber and each might be fitted with a V-shaped diiluser plate similar to diliuser plate 9. The innermost accumulator only would then be connected to the outlet pipe 5.

vAny or all the chambers or surfaces in this mufller or silencer may be partially or entirely filled, lined, and/or covered with sound-deaden ing and/or sound-absorbing material.

The drawing shows a muiiler made of sheet machine steel without showing the welds necessary to attach the various parts together. These welds were not shown in order to keep the drawing as clear as possible. Any material of suitable strength and heat-resisting characteristics would function satisfactorily. The parts might be attache-d together by riveting, hooks and slots, lock-seaming, spinning, staking, and screws, or any convenient combination of these and/or welding.

In the drawing, only a few of the perforations in parts 6, 1, B, and 9 are shown for purposes of clarity.

In the drawing, the various parts are shown as separate pieces with simple form to simplify the description of their function, while in large-scale production it would be feasible for suitably equipped plants to partly or entirely rib, corrugate, and bend the parts in order to modify their rigidity and reflective characteristics; and to construct two or more parts as shown in one piece, and thus avoid the operation of attaching them together.

It must also be noted that instead of just four receiving chambers surrounding chamber 6, any additional number might easily be added by inserting additional perforated Web plates from chamber 6 to the vertex of angular bracing plate 1 and/or 8. and the portions of the gas distrib' lil uted to each chamber can b e arranged in any desired ratio which is :dependent on the arc on chamber 6 intercepted between two successive plates, and the number of apertures and the area and shape of each.

Finally, I wish to add that a similar system of chambers, diffusers, and ducts can be arranged in both end-now and cross-flow mufilers or silencers.

I am aware that prior to my invention, muffiers and silencers have been made in which gases now through perforated chambers. I therefore do not claim such a kcombination broadly.-

The combination in a muffler of a cylindrical housing with end plates; inlet and outlet pipes passing through the centers of said end plates; an expansion chamber with a multi-perforated wall; said expansion chamber being the frustum of an oblique cone whose larger base lies in one end plate and includes the inlet pipe, andwhose smaller base lies in the other end plate and excludes the outlet pipe; an accumulator chamber; said expansion chamber contacting `the cylindri-` cal housing along an `element from one end plate to the other; said expansion chamber contact.- ing along an `opposite element to the previously mentioned element, an element of Vthe accumu4 lator chamber; the `only opening in the conical surface of said accumulator chamber being a slot from end to end made by removing Va minor arc of a circular section from one `plate to Athe other; the center line of said slot in said accumu` lator chamber being directly vOpposite theelement in contact with said expansion chamber; said accumulator chamberbeing the -frustum of an oblique cone whose larger base lies in one vendr plate and includes the outlet pipe andwhose smaller base lies in the other end plate and ex.- cludes the inlet pipe; said slot in the accumu lator chamber being iitted with a multi-perforated difuser plate attached to both sides of said slot from end plate to end plate; said diffuser plate extending into the accumulator chamber so that said diiuser plates section from end plate to end plate is V-shaped; the outer surf-ace of said accumulator chamber forming with the inner surface of said cylindrical `housing a con.- vergent passageway to the said slot in saidaccumulator chamber; multi-perforated brace plates; to the elements on either side of the `accumulator chamber midway between the .element in contact with the expansion chamber and the center lineof said slot in said accumulator chainber there being attached one face of each of said multi-perforated brace plates, the other vfaceof each of said brace plates `perpendicular to the iirst mentioned one. being attached to the ,ele-

ments on either side of the expansion chambermidway between those elements in contact with the cylindrical housing and said accumulator chamber; the ,edge of each of lsaid brace plates where both faces meet being ,attached to the cylindrical housing.

ALFRED KIMBAL.

References Cited in the tile of this patent UNITEDSTATES PATENTS 

